Evaluation of Motor Nerve Conduction Velocity in the Dog

Abstract

SUMMARY Conduction velocity (m./sec.) for fastest conducting motor fibers of canine ulnar, tibial, and fibular nerves was calculated from onset-latency differences of interosseus and cranial tibial summated motor unit potentials that were evoked by percutaneous, two-point, supramaximal nerve stimulation (indirect electromyographic method). Results (mean ± standard error) obtained with this method were 60 ± 1.1 m./sec. for the ulnar nerve (20 dogs), 60 ± 1.7 m./sec. for the tibial nerve (8 dogs), and 77 ± 3.8 m./sec for the fibular nerve (10 dogs). Conduction velocity of the tibial nerve supplying the gastrocnemius muscle was 86 + 5.1 m./sec. (4 dogs). Differences between mean conduction velocities of right and left limbs were less than 5.0 m./sec. for the nerves tested and were not significant. Bilateral measurements of conduction velocity were thus a useful means of minimizing experimental error and are of value in emphasizing presence of unilateral neuropathies. In 8 dogs, following indirect measurement of conduction velocity, nerve segments were exposed surgically and conduction velocity measured by a direct method. Results obtained by the two methods were similar. Terminal conduction times (msec.) calculated from electromyograms evoked by stimulation of the nerve near its point of entry into the muscle were 1.8 ± 0.1 msec, (ulnar nerve-interosseus muscle), 3.2 ± 0.1 msec, (tibial nerve-interosseus muscle), and 2.0 ± 0.1 msec, (fibular nerve-cranial tibial muscle).